It's tough going! The orange ring is good progress though :>
My advice is to give it several weeks of successful toilet usage in between rings, and don't hesititate to go back a stage if the cat has multiple "accidents" in a row. Also, phase out the litter very very gradually - that was one of the hardest things for fluffykins to grasp. We decided to stop at the green ring because then it's more obvious to guests that they need to leave the toilet in a certain configuration. It's easier to understand that than simply leaving the toilet seat down.